1. Field of the Invention
The invention relates to a filter cigarette.
2. Discussion of Prior Art.
The smoke of cigarettes is composed of a particle phase and a gas phase. In many filters which are employed conventionally, cellulose acetate is used for filtering the smoke. The gas phase is often not reduced to a satisfactory degree in this connection, for which reason other constructional features are also frequently adjusted. For example, it is customary to provide cigarettes with relatively high ventilation, with this resulting in the gas phase additionally being diluted with air. Another possibility for additionally reducing the gas phase is that of using gas phase-active, that is gas phase-reducing, substances in the filter. In order to determine the gas phase substances in cigarette smoke, cigarettes are usually smoked in accordance with the ISO Standard. If alternative smoking conditions are chosen, for example if the cigarettes are smoked under intense smoking conditions (see definitions below) as is customary in Canada, the gas phase values are markedly higher.
The prior art discloses filter cigarettes which use gas phase-active substances to influence the tobacco smoke so as to reduce the quantity of gas phase in the mainstream smoke which is inhaled by the smoker.
For example, filter cigarettes whose gas phase values are reduced by adding gas phase-active substances such as active charcoal are on the market. Active charcoal filters, in which the active charcoal is introduced into a chamber, have been frequently employed for a long time, in particular in Japan, and are disclosed in WO 02/37990 A2 or in other documents such as DE 42 056 58 A1 or WO 00/49901 A1.
In the case of the product “Advance”, the filter consists of a filter segment containing active charcoal and a filter segment containing ion exchange resins as well as, optionally, a mouth-end filter segment composed of cellulose acetate. Comparable cigarettes are described in WO 03/015544 A1 and WO 2004/103099 A2.
The gas phase reduction is furthermore influenced by the combination of the design parameters of a filter cigarette, with these design parameters including not only the filter additives but also the constitution of the tobacco, of the wrapping material and of the filter components.
However, a feature possessed in common by all the abovementioned previous uses and previous descriptions is that the gas phase is not reduced to a satisfactory extent in the cigarettes which are described. In the case of cigarettes which are customary in the market, the values for the total gas phase content Gtot (see below) are greater than 1200 μg/cigarette, as measured in accordance with ISO.
A high gas phase reduction is often only achieved using very high ventilation, with this then resulting in the gas phase values being extremely elevated when they are determined under intense smoking conditions.
Another disadvantage is that, after a certain storage time, conventional gas phase-active cigarette filters lose efficacy.
Other substances are frequently added either to the tobacco mixture or the filter in the case of cigarettes of the prior art, with palladium, for example being added to the tobacco as in WO 02/37990 A1. The high costs and aggravated manufacturing conditions are disadvantageous in this connection.
Elaborate and expensive multifilter constructions, involving a large number of different adsorbents or expensive special materials, are also disadvantageous.